Facebook Hacked

I have had Facebook account for years without any issues. I recently upgraded to Windows 8 Pro and did a clean install. Shortly after that my FB account started sending out vulgar messages to my friends. I have changed my password numerous times in an effort to stop the problem but it persists. I have also done a virus check with Windows Defender that came back clean..

Has anyone had this issue? I have tried going through the FB help pages but have gotten nowhere.

Any help would be greatly appreciated.

Thank you.